Project Summary/Abstract: Despite the U.S. having a Minimum Legal Drinking Age of 21 in place for nearly a quarter of a century, alcohol remains the most heavily abused substance by adolescents in the United States. It is estimated that underage drinking results in approximately 5,000 deaths from motor vehicle accidents and other causes every year, as well as a variety of health and psycho-social problems. Underage drinking parties are events that often entail high levels of drinking and alcohol-related consequences. As a result, many local communities are pursuing strategies, including party patrols, landlord lease agreements, public information campaigns, and social host ordinances, to prevent or reduce the number and size of underage drinking parties. The proposed project will use a community-based participatory approach to assess the impact of local efforts to implement a comprehensive set of environmental strategies to address underage drinking parties as a high-risk setting for youth drinking Specifically, we will partner with coalitions in 12 Intervention communities and 12 Delayed Intervention communities to build community capacity and mobilize communities to develop, implement and enforce evidence-based and promising strategies to prevent underage drinking parties. We will assess the implementation of strategies, impact on law enforcement focus on underage drinking parties, community norms regarding these parties, and awareness of potential hosts of enforcement and sanctions. We will also examine the impact of the intervention on changes in hosting behavior, youth behavior, and more distal behavioral and community outcomes. The research team at Wake Forest School of Medicine will partner with Community Anti-Drug Coalitions of America, a Coalition Advisory Board, and coalitions in 24 local communities to carry out this project.